The epithelial layer of cells of the cornea of the toad, Bufo marinus, is responsible for 95% of the active accumulation of amino acid seen in intact corneas. The accumulation of certain neutral amino acids by isolated epithelial cells is inhibited by 6-amino nicotinamide (2 mM), n-heptyl-3-hydroxyquinoline -n-oxide (0.2 mM), carbon monoxide and arsenite (2 mM). Accumulation is not significantly effected by iodoacetate, cyanide, or dinitrophenol at concentrations of 2 mM. Active amino acid accumulation is dependent upon extracellular Na ions but is relatively insensitive to ouabain. Concentrations of ouabain as high as 1 mM inhibit active accumulation only 60%. These results suggest that pathways other than glycolysis and the citric acid cycle may contribute energy for active amino acid accumulation. Active accumulation of gamma-aminoisobutyric acid is stimulated approximately 65% by 0.2 mM ascorbic acid or lactic acid. Low concentrations of oxidized glutathione (0.05 mM) have similar effects. Since it has been shown that glutathione and ascorbate are involved in the reoxidation of NADPH produced by the hexose monophosphate pathway and since this pathway is very active in the corneal epithelium, the role of this pathway in amino acid transport will be examined. Investigation into the importance of ATP levels, ATPase activity, and glucose levels in energization of amino acid transport will also be examined. BIBLIOGRAPHIC REFERENCES: Deborah F. Cooperstein and Mary C. McGahan, Amino Acid Transport in Corneal Epithelial Cells, Biochim. Biophys. Acta, in press, 1976. Mary C. McGahan and Deborah F. Cooperstein, Amino Acid Transport in Corneal Epithelial Cells, ARVO Proceedings, 1976.